During an electron beam inspection or an electron beam lithography process of the semiconductor device fabrication, the substrate surface, i.e. wafer surface, are irradiated with electron beam. If the electric contact of the substrate or wafer is incomplete during irradiation of the electron beam onto an insulator film on the wafer, a charge-up of electrons occurs wherein electrons are accumulated on the interface between the wafer and the insulator film. The charging causes deflection of the electron beam during the irradiation thereof to deform the resultant pattern in the electron beam lithography process. The charge-up restrains the signal electrons emanating from the wafer surface and thereby deforms the image of the surface in the electron beam inspection process.
There are many ways to prevent charge accumulation on wafer surface under electron irradiation. To control landing energy of the irradiating electrons, there is U.S. Pat. No. 6,734,429 of Takagi, which suggests ejecting rare gas molecules onto the wafer surface during electron irradiation; U.S. Pat. No. 6,465,795 of Madonado et al., which is irradiating laser on the wafer surface simultaneously with electron irradiation; U.S. Pat. No. 6,753,524 of Matsui et al.; and the most common way is to utilize electric contact pins to conduct excess charge away, U.S. Pat. No. 6,068,964 of Komori. The electric contact pins make physical contact to the conductive layer on the wafer backside (by means of a mechanical punch through) or a conductive path is formed between the pins and the conductive layer (by electrically breaking through the insulating layer), resulting in a stable potential which is then can be obtained on the wafer conductive layer.
With a conventional electric contact pin design, both a mechanical punch through or electrically breakthrough with an electrical pulse, may cause great damage on the backside of a wafer. These damaged places may become particle sources following up semiconductor device fabrication processes.
Accordingly, what is needed is a system and method to address the above-identified issues. The present invention addresses such a case.